when you create a table with customer addresses, and you want to select a country, then stare, then city. You have 4 tables, Tbl_Customer, Tbl_Country, Tbl_state, T_city.
In my DB is very similar, where
tbl_customers = T_qa
tbl_country = T_dept
tbl_state = T_area
tbl_city = T_equipment
those...